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Full text of "Production of aviation jet fuel from coal : staff report"

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94th Congress 1 
2d Session / 



COMMITTEE PRINT 



PRODUCTION OF AVIATION 
JET FUEL FROM COAL 



STAFF REPORT 

PREPARED FOR THE USE OF THE 

COMMITTEE ON 

AERONAUTICAL AND SPACE SCIENCES 

UNITED STATES SENATE 



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JUNE 1, 1976 



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'1-617 O 



U.S. GOVERNMENT PRINTING OFFICE 
WASHINGTON : 1976 



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COMMITTEE ON AERONAUTICAL AND SPACE SCIENCES 

FRANK E. MOSS, Utah, Chairman 
STUART SYMINGTON, Missouri BARRY GOLDWATER, Arizona 

JOHN C. STENNIS, Mississippi PETE V. DOMENICI, New Mexico 

HOWARD W. CANNON, Nevada PAUL LAXALT, Nevada 

WENDELL H. FORD, Kentucky JAKE GARN, Utah 

DALE BUMPERS, Arkansas 

Gilbert W. Keyes, Staff Director 

James T. Bruce, Professional Staff Member 

James J. Gehrig, Professional Staff Member 

Craig M. Peterson, Chief Clerk/Counsel 

Joseph L. Platt, Assistant Chief Clerk 

William A. Shumann, Professional Staff Member 

Craig Voorhees, Professional Staff Member 

Dr. Glen P. Wilson, Professional Staff Member 

Charles F. Lombard, Minority Counsel 

Earl D. Eisenhower, Professional Staff Member, Minority 

(H) 
























LETTER OF TRANSMITTAL 



U.S. Senate, 
Committee on Aeronautical and Space Sciences, 

Washington, D.C., June 3, 1976. 
Hon. Frank E. Moss, 

Chairman, Committee on Aeronautical and Space Sciences, 
U.S. Senate, Washington, D.C. 

Dear Mr. Chairman: I am transmitting herewith a staff report 
entitled "Production of Aviation Jet Fuel from Coal", the principal 
findings of which are shown in the summary on page 1. It should be 
of special interest to you that this report is a direct outgrowth of 
recommendation number 6 of Senate Report 94-633 which was pre- 
pared by the Committee. That recommendation states: 

6. Serious study should be given to the possibility of the 
development of alternative fuels such as those derived from 
coal and oil shale, synthetic hydrocarbons, liquid hydrogen, 
and nuclear propulsion. 
This new staff report indicates that the production of aviation fuels 
from the vast quantities of American coal is an alternative which 
should be given serious consideration. 
Sincerely, 

Gilbert W. Keyes, 

Staff Director. 
(in) 



Digitized by the Internet Archive 
in 2013 



http://archive.org/details/praviaOOunit 



CONTENTS 



Page 

Letter of transmittal m 

Glossary 1 

Summary 5 

1 . Liquefaction of coal 7 

2. Synthol product characteristics 8 

3. Aviation jet fuel characteristics 8 

4. Modifications of synthol process 9 

5. Process description: 

a. Coal preparation 14 

b. Coal gasification 14 

c. Gas purification 17 

d. Product synthesis 17 

e. Product recovery 19 

f. Chemicals recovery 20 

g. Aviation jet fuel treating 20 

h. Catalyst preparation 20 

6. Plant design and estimate 20 

7. Economics for aviation jet fuel production 21 

8. Conclusions 26 

LIST OF FIGURES 

Fig. 1. — Manufacture of aviation jet fuel by SASOL-Synthol process 

overall flow diagram 13 

Fig. 2. — Lurgi coal gasification building 15 

Fig. 3. — Synthol reactors of SASOL plant 16 

Fig. 4. — Rectisol gas purification unit 18 

TABLES 

Table 1. — Products from SASOL-Synthol plant modified for Aviation jet 

fuel production 21 

Table 2. — Production of oxygenated chemicals from SASOL-Synthol 

plant modified for aviation j et fuel production 21 

Table 3. — Operating costs and revenues 23 

Table 4. — Modified SASOL-Synthol plant output of coproduct chemicals.- 25 

(V) 



GLOSSARY 

Acids — Organic acids, such as formic acid, acetic acid, etc., produced 
in Synth ol reaction. 

Alcohols — Organic compounds, such as methyl alcohol, ethyl alcohol, 
etc., produced in Synthol reactor. 

Aldehydes — Organic compounds, such as formaldehyde, acetalde- 
hyde, etc., produced in Synthol reactor. 

Arge — A process developed in Germany to convert synthesis gas into 
heavy oils and waxes. 

Aromatic — A class of hydrocarbons in which carbon atoms are ar- 
ranged in six member rings like the ring in benzene. 

Benzene — An aromatic compound containing six carbon atoms and 
6 hydrogen atoms and characterized by alternate double bonds 
between the carbons. 

BPD — Barrels per day. 

Butane — A paraffin hydrocarbon containing four carbons and ten 
hydrogens in the molecule. 

BTX — A mixture of benzene, toluene and xylene. 

Cash flow — Annual profit plus annual depreciation. 

Catalyst — A material which accelerates the rate of a chemical reaction 
without itself undergoing a permanent chemical change. 

Claus — A process for converting hydrogen sulfide to sulfur. 

Converter — A reactor vessel in which materials undergo chemical 
change. 

Countercurrent — A method of contact between streams of materials 
flowing in opposite directions. 

Cyclone — A conical vessel used to classify dry powders or separate 
dust from gases by centrifugal action. 

DCF — Discounted cash flow. Sum of each year's cash flow generated 
by a project with each cash flow discounted at a selected interest 
rate to the year of start up. The sum of all DCF's over the plant 
life is set equal to the total investment committed to the plant at 
start up less salvage value at the end of plant life. 

Fractionator — A multi-stage distillation tower used to separate compo- 
nents of a mixture by successive vaporization and condensation. 

Gasifier — A reactor to convert coal to gaseous fuels. 

Gum — A shellac-like material formed by thermal decomposition of 
olefin-containing fuels. Gum can interfere with fuel feeding devices. 

Hexane — A paraffin hydrocarbon containing six carbon atoms and 
fourteen hydrogen atoms per molecule. 

Hydrocarbon — A compound of carbon and hydrogen. 

Hydrogenation — Chemical reaction involving the addition of hydro- 
gen to another chemical usually in the presence of a catalyst under 
high pressure. 

Hydrotreater — A reactor in which hydrogenation is carried out. 

Isomerization — A reaction converting straight chain hydrocarbons 
to branch chain hydrocarbons. 

(1) 



Ketones-— A class of organic compounds including a carbonyl bond 
consisting of oxygen attached through a double bond to carbon. 
Ketones are usually good solvents. 

LPG — Liquefied petroleum gas. A mixture of light hydrocarbons from 
petroleum. 

Lurgi — The Lurgi process gasifies lump coal by countercurrent contact 
with steam and oxygen rising through the coal. 

Methanation — A reaction converting synthesis gas to methane. 

MM — Million. 

Molecular weight — The weight of all the atoms contained in a mole- 
cule of a material. 

Naphtha — A light fraction of petroleum generally used as a gasoline 
component but also used as a petrochemical feedstock. 

Octane — A gasoline property that measures fuel performance in auto- 
motive engines. Also a paraffin hydrocarbon containing eight car- 
bons and eighteen hydrogens per molecule. 

Olefins — Hydrocarbons containing two less hydrogens than paraffins 
per molecule and possessing some instability with respect to gum 
formation. 

Oxygenated chemicals — Compounds of carbon, hydrogen and oxygen 
produced in the Synthol reaction and including aldehydes, alcohols, 
ketones and acids. 

Paraffins — Hydrocarbons containing maximum possible hydrogen 
and exhibiting stability to chemical reactions including gum 
formation. 

Pentane — A hydrocarbon containing five carbon atoms and 12 hydro- 
gen atoms per molecule. 

Pilot plant — Plant of a scale intermediate between laboratory-scale 
and large-scale units to evaluate integrated, continuous operations 
of chemical processes or to provide engineering design data. 

Phenol — An aromatic compound containing a hydroxyl group (an 
oxygen atom attached to a hydrogen atom) such as carbolic acid. 

Psig — Pressure in pounds per square inch gage. 

Pyrophoric — A material that burns when exposed to air. 

Rectisol — A process developed in Germany to purify synthesis gas 
prior to its catalytic conversion to hydrocarbons. 

SASOL — South African Coal, Oil and Gas Corporation, Ltd., a South 
African company operating the only commercial coal liquefaction 
plant. 

Solvent extraction — Selective transfer of specific components from one 
liquid into an immiscible solvent for ultimate recovery of the 
components. 

Standpipe — A vertical column of powder used to develop static 
pressure needed for circulation of powder through a (reactor) 
system. 

Steam reforming — A catalytic reaction to convert hydrocarbons to 
synthesis gas of which the active components are carbon monoxide 
and hydrogen. 

Straight chain — A characteristic of hydrocarbon molecules in which 
all carbon atoms are connected to adjacent carbons in a straight 
linear manner. 



3 

Synthesis — The reaction converting carbon monoxide and hydrogen 

contained in synthesis gas into hydrocarbons and oxygenated 

chemicals. 
Synthesis gas — A mixture of gases containing hydrogen and carbon 

monoxide. 
Synthol — A synthesis reaction developed in the United States and 

used by SASOL in South Africa. 
Toluene — An aromatic hydrocarbon containing seven carbons and 

eight hydrogens per molecule. 
Water gas shift — A reaction converting carbon monoxide to hydrogen 

by reaction with steam to adjust the ratio of hydrogen to carbon 

monoxide in synthesis gas for desired operation of the synthesis 

reaction. 
Weir scrubber — A process for removing sulfur oxides pollutants from 

stack gases in boiler plants. 
Xylene — An aromatic hydrocarbon containing eight carbons and 

ten carbons per molecule. 



71-617 O - 76 - 2 



PRODUCTION OF AVIATION JET FUEL FROM COAL 

(Prepared for Senate Committee on Aeronautical and Space Sciences by George T. 
Skaperdas, Pullman Kellogg, Division of Pullman Incorporated) 

Summary 

The SASOL plant was designed and has been operated in South 
Africa to produce motor gasoline rather than aviation fuel and, there- 
fore, does not furnish direct commercial demonstration of aviation 
jet fuel production from coal. But the basic Synthol process, which 
accounts for most of current SASOL production and which will be 
used exclusively in the current expansion, can be modified to maximize 
jet fuel production rather than gasoline. Using information available 
from pilot plant operations carried out during the development effort 
in Synthol in Pullman Kellogg's laboratories (then located in Jersey 
City), the product distribution to be expected when running the proc- 
ess for aviation fuel has been estimated. The results show a wide 
variety of co-products along with the jet fuel and reflect the same range 
of co-products as produced at SASOL. 

A plant to produce jet fuel from coal has been designed in a pre- 
liminary manner in order to provide an estimate of the economics for 
further evaluation of this system. A plant charging 17,100 tons per 
day of coal and producing some 9,400 barrels per day of jet fuel will 
require a total investment of 780 million dollars and will produce jet 
fuel that would have to be sold at 76 cents per gallon to provide a 
15 percent discounted cash flow rate of return on the investment. Such 
commercial operation is difficult to justify as long as petroleum jet 
fuel remains available at less than half this price. But jet fuel produc- 
tion from coal could be set up as a matter of national security to 
minimize the dependence of aviation jet fuel on petroleum which is 
being imported at an increasing rate. Under these conditions, funds 
for construction could be supplied by the Government and no return 
on these funds would be required of the operation. The resulting fa- 
cility could then be operated under contract and jet fuel could be 
supplied to the Government at no cost by the contract operator who 
would have as his incentive income from sale of byproduct chemicals. 

This incentive seems attractive for a single plant producing some 
2 percent of the Nation's military aviation fuel. If ten plants were to be 
considered in order to provide 20 percent of the nation's needs for 
military jet fuel, disposal of chemicals may raise some problems par- 
ticularly with ethanol. Several methods of handling these problems 
appear to be available. 

(5) 



1. Liquefaction of Coal 

Conversion of coal to hydrocarbons can be of national interest because 
such conversion can free important national energy requirements from 
dependence on imported petroleum and can then supply these energy 
needs from abundant, indigenous coal. 

This is particularly important in the case of aviation jet fuels. These 
are currently derived from petroleum which is now significantly and 
increasingly dependent on imports. Thus a prolonged embargo by 
overseas petroleum exporters could seriously impair ready availa- 
bility of aviation jet fuels for both civilian and military use. Conver- 
sion of coal to hydrocarbon liquid fuels suitable for aviation does, 
therefore, merit consideration as a means of providing freedom from 
disruption of aviation due to unfriendly actions of oil exporting 
countries. 

Coal has been converted into hydrocarbon liquid fuels either by 
complete gasification followed by synthesis or by hydrogenation. 
Hydrogenation was widely used in Germany during World War II 
to produce liquid hydrocarbons but the processing conditions are 
severe and this process approach is no longer being used in any 
commercial-scale operation, having been abandoned in the post-war 
period. Development work is currently underway in several labora- 
tories to improve the hydrogenation method by carrying out the reac- 
tions very rapidly. This will serve to retain hydrocarbon structures 
that occur naturally in coal and thus minimize the chemical work 
that must be done in synthesizing liquid hydrocarbons. But this effort, 
though potentially promising, is in the early research stages and is 
not available for the near future. 

In contrast the gasification-synthesis approach has been in com- 
mercial use for two decades at a plant of the South African Coal, 
Oil and Gas Corporation, Ltd. (SASOL) in South Africa. In this 
operation coal is essentially completely gasified to synthesis gas 
which is largely a mixture of carbon monoxide and hydrogen. The 
synthesis gas is then converted to liquid hydrocarbons by reaction in 
the presence of a suitable catalyst. Conversion of the coal substance 
to simple gases does require substantial energy but the synthesis 
step does make it possible to make a more closely controlled liquid 
product that is not burdened with the more complex molecular frag- 
ments that are produced from coal by direct hydrogenation. Thus a 
cleaner fuel is possible from synthesis and costs of purifying or up- 
grading hydrogenation product are not necessary. 

The synthesis approach goes back to experiments reported in 1923 
by Franz Fischer and Hans Tropsch on their work at the Kaiser 
Wilhelm Institute. This early work dealt with catalyst preparation 
and catalyst properties since the catalyst proved to influence the 
course of the synthesis reaction very significantly. Further develop- 
ment of the process led to the Arge process which used a pelleted 

(7) 



8 

cobalt-based catalyst held in tubes. The Arge synthesis is used at 
SASOL to produce relatively small quantities of lubricating oils 
and waxes composed of paraffins, products also produced by this 
route in Germany during the war. A second development of the 
Fischer-Tropsch chemistry was completed by Pullman Kellogg in its 
laboratories some thirty years ago. This development, known as the 
Synthol process, uses an iron catalyst in powdered form and circulates 
t he catalyst at high flow rates together with the synthesis gas through 
the reactor. Improved process and temperature control provided by 
the Synthol catalyst and reactor design permits better control of 
product characteristics and the Synthol process has been used at 
SASOL to produce most of the product output, which is largely motor 
gasoline. The SASOL plant is now being expanded very substantially 
after some twenty years of operating both the Arge and Synthol 
syntheses. It has been reported that the Synthol process will be 
used exclusively in the planned expansion. 

2. Synthol Product Characteristics 

The Synthol process was developed to produce motor gasoline which 
is the major Synthol product at SASOL. This motor gasoline is quite 
high in olefins which account for 60-70% of the material in the gaso- 
line. The olefins are desired for motor gasoline because they provide 
a much better octane rating than is provided by paraffins made in the 
Arge process. In addition to gasoline, the Synthol process produces a 
spectrum of other products ranging from methane (which can be sold 
as substitute natural gas) through light olefins (basic petrochemicals) , 
light paraffins (petrochemical feedstock or LPG), naphtha or motor 
gasoline, diesel fuel and some wax. In addition to these hydrocarbons, 
Synthol produces oxygenated straight chain organic chemicals such as 
aldehydes, alcohols, ketones and acids. Thus, the Synthol process 
produces a variety of byproducts along with its major gasoline 
product. The same is true of the Arge synthesis. 

But the product distribution of the SASOL operation does not con- 
tain any aviation jet fuel and, as a result, the two decades of commer- 
cial coal liquefaction experience at SASOL cannot be used directly 
to evaluate the gasification-synthesis approach for converting coal 
to aviation jet fuel. 

3. Aviation Jet Fuel Characteristics 

There are several important differences between SASOL or Synthol 
gasoline and aviation jet fuel. First, the hydrocarbon molecules of 
aviation jet fuel are larger, containing more carbon atoms. Gasoline, 
for instance, contains hydrocarbons ranging from butane (four 
carbons) to dodecane (twelve carbons) while aviation jet fuel contains 
hydrocarbons up to at least hexadecane (sixteen carbons) . As a result, 
jet fuel has the advantage of a higher flash point and is, therefore, 
less subject to fire from accidental sources of ignition during use or 
storage. 

The hydrocarbons of Synthol gasoline are largely olefins and thus 
provide the necessary octane rating to prevent engine knock in auto- 
motive internal combustion engines. This advantage of olefins, how- 



9 

ever, is accompanied by the disadvantage of relative instability to 
gum formation at the higher temperatures prevailing in the fuel 
systems of jet engines. As a result, an olefin specification of less than 
1% has been set for aviation jet fuel. It may be noted that this specifi- 
cation has been set for olefin content of petroleum materials that con- 
tain olefins produced by cracking reactions. These reactions produce 
small quantities of diolefins which form gums very much more readily 
than do olefins and the low olefin specification may reflect the un- 
wanted characteristics of accompanying diolefins more than the 
inherent instability of olefins themselves. The Synthol olefins are free 
of diolefins and may, therefore, be much more acceptable than the 
more familiar, but contaminated, olefins produced by cracking petro- 
leum. Since Synthol olefins have not been considered or used for avia- 
tion jet fuel there is no information on their performance in jet engines 
and it appears best, at this time, to accept the 1% limitation on olefins 
even though this may, in fact, be unnecessary. 

Olefins can be hydrogenated to paraffins in order to meet the olefin 
specification for jet fuel stability but this increases the freezing point 
of the hydrocarbon. It becomes necessary, therefore, to consider what 
further processing of the Synthol product, after its hydrogenation may 
be needed in order to meet aviation jet fuel freezing point specifications. 

4. Modifications of the Synthol Process 

A number of modifications of the SASOL-Synthol operations are 
necessary in order to meet the three requirements of aviation jet fuel, 
namely (1) larger or heavier hydrocarbons containing more carbon 
atoms in the molecule (2) very low olefin content to provide stability 
against gum formation and (3) satisfactorily low freezing point. 

The extensive research and development program on the Synthol 
process carried out in the laboratories of Pullman Kellogg some thirty 
years ago prior to the SASOL project has shown that the size of the 
hydrocarbon molecules produced can be varied over a wide range by 
changing the catalyst composition and the reaction conditions imposed 
on the synthesis reaction producing the hydrocarbons. The following 
tabulation illustrates this by showing how the distribution between 
gasoline molecules and heavier molecules, including jet fuel molecules, 
varied in one set of tests. 





TEST CONDITION 










Percent 




A 


B 


C 


D 


Gasoline in product 

Heavier than gasoline 




94.4 
5.6 


88.4 
11.6 


84.4 
15.6 


70.6 
29.4 









These results, all obtained on one of the many catalysts studied, 
show that conditions selected for the reaction can effect a very sub- 
stantial change in product distribution, increasing the portion of 
product containing jet fuel from 5.6% to better than 29.4% of the 
hydrocarbons produced. Furthermore, modest changes in catalyst 
formulation also provide substantial additional changes in hydro- 
carbon molecular weight distribution further increasing the ability to 
maximize aviation jet fuel production. Review of these factors has 



10 

led to the conclusion that the Synthol process can be modified to yield 
a hydrocarbon mixture having the following distribution of naphtha 
(essentially motor gasoline), aviation jet fuel and the still heavier fuel 

°ih Percent 

(by volume) 

Naphtha 27 

Aviation jet fuel 50 

Fuel oil 23 

. Total 100 

From this liquid product distribution and the demonstrated varia- 
tion of other products as the liquid product yield varied, an overall 
product composition expected for aviation jet fuel production was 
estimated and is shown in Table 1 in Section 6 of this report. The 
variety of co-products is illustrated in this table. 

It may be noted that this desired distribution of hydrocarbons was 
not produced in any test operation in the Synthol development 
program. The objective of that program was to maximize motor 
gasoline and the research, therefore, concentrated on this objective. 
Variations in test conditions did, however, show that jet fuel com- 
ponents can be increased substantially relative to gasoline, and the 
knowledge of Synthol reactions provided in the development program 
makes it possible to conclude with confidence that the proposed jet 
fuel operation can be achieved successfully. 

Should the decision be made to proceed with a project to make jet 
fuel from coal it will be necessary to confirm the proposed product 
distribution. A relatively short development program should be suffi- 
cient, however, to provide the necessary confirmation of the projected 
product distribution. 

Such a program will require a minimum level of effort if the hydro- 
carbon type of molecules produced is the same as the SASOL material 
and only the size of the molecules is increased. Under these conditions 
the product in the aviation jet fuel range of molecular weights will 
contain some 60% to 70% olefins. As already pointed out, this is 
unsatisfactory for aviation jet fuel because of relative instability of 
olefins with respect to gum formation. Reference to the Standard 
Specifications for Aviation Turbine Fuels (ASTM Designation: D 
1655-73) shows that olefins in aircraft turbine fuels should be limited 
to about 1 percent or less. It is, therefore, necessary to hydrogenate 
the raw jet fuel from the modified Synthol process to convert the 
olefins to paraffins. This hydrogenation requires hydrogen which, 
fortunately, can be made from co-product methane produced in the 
Synthol reactor. Conversion of methane by reaction with steam in a 
conventional reformer furnace to a hydrogen-rich gas which can then 
be refined to essentially pure hydrogen is a well-known, thoroughly- 
demonstrated industrial operation. Furthermore only a modest 
portion of Synthol-produced methane is needed to generate the 
necessary hydrogen so that it is not necessary to import hydrogen into 
the proposed plant. In addition the hydrogen manufacturing process, 
itself, and the Synthol olefin hydrogenation process, also a well-known 
industrial operation, require very little additional capital and impose 
very little economic burden on the conversion of coal to aviation jet 
fuel. Consequently the facilities proposed for evaluating production of 
jet fuel from coal include a hydrogen manufacturing plant and an 



11 

olefin hydrogen ation plant and all the necessary support facilities 
making use of plant-produced methane as the source of hydrogen. No 
experimental test or demonstration program is considered to be neces- 
sary for these two units. 

When Synthol olefins are hydrogenated the paraffins produced will 
easily pass the gum stability test specification. The skeletal structure 
of the paraffins will depend on the structure of the olefins produced in 
the Synthol reactor and, as a result, the paraffins will be a mixture of 
normal paraffins and isoparaffins. (In normal paraffins the carbon 
atoms of the molecule are attached to each other in tandem in a 
straight line while in isoparaffins one or more of the carbons are 
attached to the remaining straight-chain carbons as branches off the 
straight line). The normal paraffins in the jet fuel range have boiling 
points some 70°F above the freezing point of — 58°F specified for 
aviation jet fuel in ASTM D 1655-73. The isoparaffins have freezing 
points, fortunately, that are up to 100°F below the freezing points of 
normal paraffins. Thus isoparaffins will easily meet the freezing point 
specification. The actual jet fuel material will be a blend of normal 
and isoparaffins reflecting the comparable olefin type distribution in 
the untreated Synthol jet fuel fraction. The actual concentration of 
the two types for the jet fuel materials to be produced by the modified 
Synthol process is not known in full detail. Consequently it appears 
prudent for the current technical and economic evaluation study to 
include the process step of isomerization of the Synthol jet juel 
material after hydrogenation. This should ensure the presence of 
sufficient branch chain isomers to permit the jet fuel to meet the 
freezing point specification. 

Isomerization of normal paraffins has been practiced commercially 
for almost four decades. The hydrocarbons isomerized commercially 
have ranged from four to six carbon atoms per molecule and thus are 
lower in molecular weight than the jet fuel material which ranges 
from eleven to sixteen carbon atoms per molecule. Though no com- 
mercial demonstration is available for isomerizing the jet fuel range of 
normal paraffin hydrocarbons (there has been no commercial need for 
such a reaction when dealing with petroleum-derived materials), the 
reaction is a relatively simple one. It seems probable that a suitable 
isomerization process can be demonstrated easily starting with the 
established isomerization technology on lighter hydrocarbons and can 
then be used to meet freezing point specifications. 

A further approach is available to meet the freezing point specifi- 
cation. This reaction is polymerization and has also been demonstrated 
commercially for many years. In this approach the lighter portion of 
the gasoline-range naphtha can be separated out and can then be 
polymerized into the heavier jet fuel range of hydrocarbons. In this 
case the two smaller straight chain olefins combine to make larger 
branch-chain olefins. When these compounds are hydrogenated, branch- 
chain paraffins are produced of much lower freezing point than the 
straight chain equivalents formed directly in the Synthol reactor. This 
route is also available to meet the low freezing point specification. In 
addition, this incremental process step can transfer some 1,300 barrels 
per day of hydrocarbons from naphtha to aviation jet fuel, increasing 
the jet fuel production from 9,381 to about 10,600 barrels per day. 



71-617 O - 76 - 3 



12 

In addition, incorporation of selected aromatics into the hydro- 
genated and isomerized jet fuel is available to lower the freezing 
point still further. Thus, the ASTM specification permits 20% 
aromatic content by volume in aviation jet fuel. Substituted benzenes 
except for the xylenes have low freezing points and these materials 
will be available in the benzene-toluene-xylene fraction (BTX) that 
will be distilled from coal along with tar in the upper part of the 
slagging Lurgi gasifiers used in the process sequence adopted for this 
study. It is a simple operation to recover low freezing point aromatics 
by simple fractional distillation from the BTX and use these to 
depress further the freezing point of the jet fuel product. This would 
also provide some increase in jet fuel output. From the aromatics 
condensed out of the coal gasification unit an additional 400 barrels 
per day could be blended into the aviation jet fuel which would then 
be produced at the rate of 11,000 barrels per day. 

It is clear that a number of alternate process steps are available to 
decrease the freezing point of the hydrogenated jet fuel material 
produced by the Synthol process. These alternates include isomeriza- 
tion, addition of polymer made from the light naphtha and addition 
of aromatics. Additional study, probably including some experimenta- 
tion with actual Synthol fractions will be needed to select the best of 
the alternates which may turn out to be a combination of these 
possibilities operating each at a partial level of conversion to obtain 
best performance. 

Still another alternate that is possible and may prove most economic 
is to use insulation and engine exhaust gases to maintain the aircraft 
jet fuel tanks at a temperature above the high altitude levels so that 
the hydrogenated olefins are satisfactory with no further processing. 
Such a temperature may be about +40°F if no further processing is 
adopted, but, again, a combination of some insulation and some 
processing may prove most economic. 

Of the several alternates available for meeting all aviation jet 
fuel specifications, the following combination has been selected for 
the current evaluation. The olefins from the modified Synthol process 
will be hydrogenated and then isomerized. Facilities for making hydro- 
gen from part of the fuel as produced in the plant will also be included. 
This arrangement is felt to provide an evaluation of reasonable, though 
less than maximum, aviation jet fuel production. As a result a con- 
servative evaluation should result. Furthermore the petroleum 
industry technology that is to be modified for use in the proposed 
plant has been developed to a high degree of sophistication and it is 
reasonable to conclude that the necessary technology adaptations of 
hydrogenation and isomerization can be developed with a very high 
degree of probability of success and at modest cost. 

5. Process Description 

The overall plant arrangement required for converting coal to 
aviation jet fuel and the accompanying co-products is shown in 
Figure 1, which shows the relationship of the Synthol unit to the 
many other units that must be operated with the Synthol unit. 



13 



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Figure 1. — Manufacture of aviation jet fuel by SASOL-Synthol process overall 

flow diagram. 



14 

(A) COAL PREPARATION 

Coal delivered to the plant site goes first to a coal preparation unit 
where it is crushed and dried to 2 percent moisture content. A portion 
of the coal is transferred to the steam plant to be used for generating 
utility steam required in all other operating units of the plant. Flue 
gases from the steam plant are treated in a Weir Scrubber which re- 
moves sulfur oxides to permit compliance with air quality standards 
and also removes fly ash that has escaped the precipitators. Limestone 
is fed to the Weir Scrubber and sludge is discharged for disposal. 

(B) COAL GASIFICATION 

The major portion of the crushed, dried coal is transferred to the 
Coal Gasification Unit where it reacts with oxygen generated in an 
Air Separation Unit and steam generated in the steam plant. Lurgi 
gasifiers have been. used in the proposed plant for this study, but 
operation with ash slagging has been postulated. In contrast, the 
Lurgi gasifiers (See Figure 2 for example.) used at SASOL operated at 
lower temperatures and discharged a granular ash. Slagging operation 
is being successfully demonstrated in a Lurgi gasifier that had been 
used commercially at Westfield, Scotland before its dedication to this 
development program. This program is sponsored by a group of 
American Companies and is being conducted by the British Gas 
Corporation with some participation by Lurgi. The more modern 
slagging operation was selected for this study because it offers eco- 
nomics in both capital investment, operating costs and the necessary 
environmental control facilities in comparison with the Lurgi gasifiers 
discharging a granular ash as installed at SASOL for operation in 1952. 
The selection has been made on the premise that slagging operation 
will be fully demonstrated by the time that plans for a coal-based 
aviation jet fuel plant can be completed. This seems reasonable in 
view of the fact that two runs of 1-week duration have already been 
successfully completed and a longer run is in the final stages of prep- 
aration. Ash slag flows from the bottom of the reactor to be quenched 
in water. The resulting slurry of ash is then transferred to disposal. 
Raw synthesis gas produced by the gasifiers leaves the top of the 
gasifier after countercurrent contact with the feed coal which is charged 
to the top of the gasifier and flows downward. This contact reduces 
the temperature of the gas from temperatures approaching 2000°F 
where gasification is occurring to about 1000°F at the top gas outlet. 

The raw gas is composed primarily of carbon monoxide and hydro- 
gen along with some methane and carbon dioxide from gasification, 
but to these components are added distillation products from coal 
generated by distillation of the coal before it reaches the gasification 
zone. These components include aromatics such as benzene, toluene, 
xylene (BTX), gasoline, heavier oils and tar. In addition the gas 
contains unconverted steam as well as sulfur and nitrogen contami- 
nants. This gas requires important purification and adjustment before 
it can be used as a satisfactory synthesis gas in the Synthol reactor. 
(See for example, Figure 3, page 16.) 



15 







Figure 2. — Lurgi coal gasification building — Steam generation in background. 



16 




17 

(C) GAS PURIFICATION 

The first step in gas purification is cooling including recovery of 
some of the heat content in a waste heat boiler which supplements 
the coal-fired steam generator. Tar is condensed out of the gas on 
cooling and is used as additional fuel in the steam plant and then the 
lighter hydrocarbons, which are highly aromatic, are separated out 
and sent to the Product Recovery section of the plant. In addition a 
phenolic, oily water is condensed from the gas during cooling and this 
water stream flows to a solvent extraction plant where phenol is 
extracted from the water for sale. The extracted water then enters 
a secondary treatment plant where it is further purified so as to meet 
effluent control standards before being discharged from the plant. 

Gas leaving the cooling section of the Gasification Unit then flows 
to the Gas Purification Unit where it first undergoes water gas shift 
reaction. Here the carbon monoxide content of the gas is reacted with 
steam to generate hydrogen and carbon dioxide. The purpose of this 
operation is to raise the ratio of hydrogen to carbon monoxide in the 
subsequent synthesis gas to permit effective use of the synthesis gas 
in chemical conversion to liquid products. Following water gas shift, 
the gas flows to a Rectisol unit where sulfur and nitrogen compounds, 
final traces of gum-forming compounds and excess carbon dioxide 
are removed. Purification in the Rectisol unit is provided by counter- 
current washing of the contaminated gas with a refrigerated, re- 
generated methanol stream. (See for example Figure 4.) The recovered 
sulfur compounds, mostly hydrogen sulfide, are converted to sulfur in 
a Claus unit. 

(D) PRODUCT SYNTHESIS 

Gas leaving the Rectisol unit now contains hydrogen and carbon 
monoxide in the right ratio together with some methane, carbon diox- 
ide and nitrogen. This highly purified synthesis gas is now ready for 
reaction in the Synthol unit and is fed to the suction of the synthesis 
converter recirculating blower, where it is combined with the washed 
gas leaving the converter system. The combined gas streams are pre- 
heated in a heater exchanger by the oil slurry circulated over the 
product scrubber and enter the bottom part of a Kellogg converter. 
The high velocity gas stream entrains the desired amount of iron 
catalyst fed to it through a slide valve. The gas carrying the suspended 
particles flows upward through the reactor body. The reactor body is 
provided with heat exchanger coils through which cooling oil is 
circulated maintaining a temperature of about 600°F in the reactor 
space. Hot oil is cooled in a waste heat boiler where it generates 450 
p.s.i.g. steam which is used to drive the main power consumers in the 
Synthol plant and also provides heating steam for reboilers in the 
product recovery section. 

Reacted gases carrying the catalyst leave at the top of the converter 
and enter the catalyst settling hopper in which the bulk of the cata- 
lyst is removed from the reaction gases. The gases then pass through 
a system of cyclones in which most of the fine particles remaining in 
the gases are knocked out. The combined streams of the catalyst fall 
by gravity into a vertical leg from which they are reintroduced into 
the gas stream entering the converter through the slide valve men- 
tioned above. Fresh catalyst is introduced into the bottom part of the 
stand pipe and used catalyst removed from its upper part. 



18 




19 

The gases leaving the cyclones enter a scrubber in which they are 
washed by recirculating oil. The temperature in the scrubber is con- 
trolled so that the gases leaving the top of the scrubber would con- 
tain all of the desired products. The sensible heat removed from the 
hot gases by the recirculating oil is used to preheat the reactor feed 
gas and boiler feed water entering the waste heat boiler. Catalyst 
nnes collected in the oil are returned to the reactor body as a sus- 
pension in oil. Heavy oil collected in the lower part of the scrubber 
is taken to the vacuum flash tower in the recovery section. Hot gases 
leaving the top of the tower are cooled first in a Boiler Feed Water 
heater, and finally to 100°F in a condenser. Condensate and cooled 
gases enter the wash tower in which the liquid products are separated 
from the gas stream. 

Liquid products from the wash tower are taken to the oil wash tower 
where synthesis products soluble in water are washed out of the oil 
by a counter-current stream of process water. Washed oil from this 
tower flows to the oil treaters in the recovery section. Wash water 
from the oil wash tower is combined with wash water from the wash 
tower and is taken to the recovery section for separation of soluble 
chemicals. These chemicals are mainly lower alcohols, aldehydes, 
ketones, and acetic and propionic acids. Washed gas from the top of 
the wash tower is separated into two streams: recycle and product. 

The recycle stream passes through a mist entrainment separator 
drum, is combined with the fresh feed gas, as mentioned above, and 
returned by the recycle compressor to the bottom of the synthesis 
converter. The product gas stream passes through another mist 
separator drum for removal of droplets and enters a scrubbing sys- 
tem in which C0 2 is removed from the gases which are then taken 
to the product recovery section. 

(E) PRODUCT RECOVERY 

The product gas leaving the C0 2 removal system is compressed to 
about 600 psig, last traces of C0 2 removed by scrubbing with a 
sodium hydroxide solution, water is removed in gas driers and the 
dried gas is chilled in a multistep chilling system to about — 200°F. 
At the lowest temperature, light gases are flashed off, and then step- 
wise, methane, and mixtures of ethylene-ethane, propylene-propane, 
butylene-butane are flashed off, and finally the liquid containing 
pentanes and higher hydrocarbons is directed towards the fractionator. 
Liquids separated in the first chilling steps are passed over a liquid 
drier to the methane removal step. In the fractionator, gasoline, the 
aviation jet fuel fraction and fuel oil products are separated. Washed 
light oil from the synthesis section is combined with the overhead 
from the vacuum flash tower, is vaporized and passed over silica- 
alumina catalyst to raise the octane number of the gasoline compo- 
nents; some cracking of the oil takes place, and olefins are produced. 
Effluent from this treatment is cooled and condensed and the liquid 
introduced into the main fractionator column. Bottoms from the 
fractionator are combined with the heavy oil separated from the 
product gases in the scrubber, and introduced into the Vacuum 
Flash Tower. Overhead from this tower is taken to the silica-alumina 
catalyst reactor, as mentioned above, the bottoms are the fuel oil 
product. 



20 



(F) CHEMICALS RECOVERY 



The combined wash water streams are taken to the Primary Dis- 
tillation Tower; alcohols, ketones and aldehydes are distilled over- 
head, and separated into desired individual products in distillation 
towers. Main product is ethanol; propanol, butanol, higher alcohols, 
acetones, acetaldehyde and methyl-ethyl ketone are also produced. 
Bottoms stream of the distillation tower is mixed with ethyl acetate 
in a system of extractors. Acids dissolve in ethyl acetate, the solution 
is separated from water, ethyl acetate recovered and organic acids 
separated by distillation. Main product is acetic acid; some propionic 
acid and higher homologs are also formed. 

(G) AVIATION JET FUEL TREATING 

The aviation jet fuel fraction produced in the Synthol reactor is 
transferred to a final treating section to produce specification grade 
product. Here the material is treated with hydrogen in a hydro- 
treater unit over a cobalt-molybdenum catalyst to reduce olefins to 
less than 1 %. Hydrogen for this purpose is generated in this section 
of the plant from natural gas using the known combination of steam 
reforming, water gas shift, carbon dioxide removal and methanation. 
Methane for this purpose is available from the Product Recovery 
section of the plant. The hydrogenated stream is finally isomerized 
to produce isoparaffins that will permit freezing point requirements 
to be met. 

(H) CATALYST PREPARATION 

The catalyst used in the Kellogg Synthol Process is basically pure 
metallic iron. Because its life is short (about 60 days) and large 
amounts are needed, catalyst preparation is considered as part of the 
overall plant. Mill scale or magnetic ore are fused in an electric fusion 
furnace at 3000°F, activators added, and fused product is quenched 
in water, ground, and reduced to metallic iron by a stream of pure 
hydrogen prepared in the plant. The catalyst is pyrophoric and must 
be kept under an inert or reducing atmosphere. 

6. Plant Design and Estimate for Evaluation of Economics 

A preliminary plant design was selected, using the sequence of 
operations described in the preceding section, to serve as a basis for 
economic evaluation of aviation jet fuel produced from coal. This 
plant will require a coal supply of 17,100 tons per day of a coal having 
an ash and moisture content of 10.2% and 10% respectively and a 
heating value of 11,030 Btu per pound when dried tc 1% water con- 
tent. These coal characteristics are readily available at the location 
of the plant design used in this study. 

The net production of materials, after allowing for all internal con- 
sumption within the plant, including the hydrogen, hydrogenation and 
isomerization units, is shown in Table 1. The oxygenated chemicals 
produced in the plant are shown in Table 2 along with the revenues 
that can be generated by the chemicals when sold at typical market 
prices. 

The investment in the completely erected plant ready for operation 
has been estimated to be $780,000,000 in current dollars. This in- 



21 

vestment includes all the process units needed to prepare coal, gasify 
it, purify the gas, synthesize the products and, finally, recover the 
products for sale. In addition, all offsites including all utilities gener- 
ation, effluent control facilities, plant utility distribution systems, 
maintenance facilities and product storage and handling are included 
in the estimated cost of the plant, Thus all costs necessary to operate 
the plant on run-of-mine purchased coal have been included. 

The overall plant, containing fourteen individual units as shown on 
the block flow diagram of Figure 1, requires a substantial amount of 
processing to upgrade coal to the clean fuels and chemicals that are 
produced. Each step is designed with due attention to energy con- 
servation and the overall energy efficiency is 64%. That is, the heating 
value of all the products is 64% of the heating value of all the coal fee- 
to the plant. 

The plant design selected for this study required a water supply of 
some 30,000 gallons per minute or about 40,000 acre feet per year. 
This water is used for process cooling since water was readily available. 
In other areas where water may be less available, air cooling can be 
used for process purposes and the water requirement can readily be 
brought down to about 5,000 gallons per minute or 7,000 acre feet 
per year. 

Table 1. — Products from SASOL-Synthol plant modified for aviation jet fuel 

production _ 

Pound* per 
hour 

Fuel gas (6,450,000,000 Btu per day) 14, 335 

Substitute natural gas (4, 130,000,000 Btu per day) 8, 835 

Ethylene 10, 034 

Liquefied petroleum gas (6,950,000,000 Btu per day) 14, 335 

Propylene 34, 045 

Butylene- Butane 17, 560 

Gasoline (5054 BPD) 53,039 

A-l aviation jet fuel (9,381 BPD) 109,662 

Fuel oil (4350 BPD) 55, 548 

Oxygenated chemicals 50, 172 

Sulfur 48,738 

Benzene, toluene, xylene, gasoline, oil (18,200,000,000 Btu per day) 37, 987 

Total 454,290 

TABLE 2.— PRODUCTION OF OXYGENATED CHEMICALS FROM SASOL-SYNTHOL PLANT MODIFIED FOR AVIATION 

JET FUEL PRODUCTION 





Pounds per 


Annual 




hour 


income 


Acetaldehyde 


810 


$960,000 


Methanol 


216 


256,000 


Acetone 


2,500 


2, 760, 000 


Methylethyl ketone 


925 


1,310,000 


Ethanol 


27,500 


18, 400, 000 


Propanol 


6,060 


11,000,000 


Isobutanol 


844 


1,400,000 



Pounds per 
hour 



Annual 
income 



Normal butanol 2,030 2,720,000 

Heavy alcohols 2,950 6,970,000 

Acetic acid 4,570 5,950,000 

Propionic acid 1,040 1,470,000 

Higher acids.. 720 1,700,000 

Total 50,172 54,896,000 



7. Economics for Aviation Jet Fuel Production 



Economic factors in the operation of the selected plant are summa- 
rized in Table 3, which lists all operating costs, including return on 
investment, and balances these costs against revenues to be earned 
from all the co-products made in the operation. 



22 

A coal cost of $5.00 per ton has been used in the economic evaluation 
of the plant set up for aviation jet fuel production. This is a lower 
price than the average price of $15.46 per ton, including delivery- 
charges, paid by the electric utility industry or the average price of 
$15.75 per ton, f.o.b. mines, paid by all users of coal in the United 
States in 1974. The $5.00 price is judged, however, to be more reason- 
able because of the following considerations. It is highly unlikely that 
the very large investment in the coal conversion processing plant will 
ever be made without a very strong assurance that dependable, unin- 
terrupted supply of coal at an acceptable price is available through 
the life of the plant. Such assured supply essentially mandates the 
commitment of a mine of sufficient size to serve this coal conversion 
plant and no other customers so that unforeseen and uncontrollable 
market factors do not interfere with continued, dependable supply of 
coal. As a matter of interest, the three proposed coal gasification plants 
designed to produce pipeline quality substitute natural gas (SNG) 
commercially have all been set up with an adjacent coal mine dedi- 
cated fully to the individual SNG plant. Applications to the Federal 
Power Commission in connection with these three plants have de- 
tailed the cost to the plant of coal produced by the dedicated mine. 
The most recent of these applications, made early in 1974, details all 
mining costs including taxes, royalties and capital return, and reports 
a total cost of coal delivered to the process plant of $4.25 per ton. The 
mine capacity for the SNG plant is about the same as for the aviation 
jet fuel plant and the cost of coal to the two plants should, therefore, 
be comparable. Allowing about 20% escalation since the SNG coal 
cost figure, it is concluded that $5.00 per ton is a reasonable cost for 
coal to the liquefaction plant. In this connection, it may be of interest 
to note that a recent report by the Council on Wage and Price Sta- 
bility concluded that surface-mined coal should be rather stable in 
price and should be available at $5.00 to $6.00 per ton f.o.b. mine for 
the next decade, regardless of how much coal demand should increase 
in this period. 

In any event, coal cost will depend on mine location and mine char- 
acteristics and a definitive coal cost can only be determined for a specific 
site at the time of operation. Until such factors have been determined 
it does appear that $5.00 per ton is a satisfactory figure for economic 
evaluation of the proposed operation. Furthermore, the cost of coal is 
not a major item in the estimated cost of jet fuel. The effect of coal 
cost on jet fuel price is shown later to be a modest one. 

Finally, coal consumption by the proposed plant is equivalent to that 
of a conventional electric utility, generating 1700 megawatts. 

The cost of catalyst and chemicals consumed in the plant as well as 
the labor required have been estimated by itemizing and adding indi- 
vidual requirements for each of the dozen odd units in the overall 
plant. Overhead and maintenance and local taxes and insurance costs 
are judged to be typical values. Capital return is based on 15 percent 
discounted cash flow (DCF) return of all investments less salvage 
value after the life for the plant assumed to be 20 years. Total invest- 
ment used in the calculations included working capital and interest 
over the three-year period assumed for construction of the plant. 

The figures in Table 3 show clearly that capital return and Federal 
income tax are the most important cost items, the two together ac- 
counting for almost 76 percent of total operating costs. 



23 

Distribution of costs among the eight major products listed in Table 
3 may, of course, be made in a number of ways. The specific method 
used in Table 3 used the following bases. First, the olefins were as- 
sumed to be sold at typical values of 12 cents, 10 cents and 6.2 cents 
per pound, respectively, for the ethylene, the propylene and the 
butylene-butane mixture. The oxygenated chemicals were assumed to 
bring in the revenues shown in Table 2 while sulfur was set at a value 
of $40 per long ton and the BTX, gasoline and oil were taken at 8 
cents per pound. The remaining revenues needed were derived from 
the individual liquid and gaseous fuel streams assuming each fuel to 
be sold at the same value per unit of heating value. 

On this basis the three liquid fuel streams would have to be sold at 
the following prices. 

Cents 
per gallon 

Aviation jet fuel 76 

Motor gasoline 69 

Fuel oil 85 

The price of 76 cents per gallon for aviation jet fuel may be compared 
with spot prices for refined petroleum products in intrastate commerce 
as published weekly by the Oil and Gas Journal. For kerosene, which is 
largely used for aviation jet fuel, these spot prices have been ranging 
recently from about 30 cents to 34 cents per gallon. Thus the modified 
SASOL-Synthol operation bears a very heavy burden if it must 
earn a capital return characteristic of industrial operations. 

If the plant were to be operated at 10 percent DCF rate of return, 
the aviation jet fuel price at the plant would drop to 44 cents per 
gallon but if 20% DCF were needed, the jet fuel price would become 
$1.15 per gallon. These figures simply emphasize the sensitivity of jet 
fuel price to the rate of return because of the extremely high capital 
intensity of this coal-based operation. Even at 10 percent DCF rate 
of return, which seems low for the very large risks involved, the price 
of aviation jet fuel is too high to justify commercial investment and 
operation of the proposed coal conversion facility. 

TABLE 3— OPERATING COSTS AND REVENUES SASOL-SYNTHOL PLANT MODIFIED FOR AVIATION JET FUEL PRO- 
DUCTION: PUNT INVESTMENT, $783,000,000; PLANT OUTPUT PER TABLES 1 AND 2 

Amount 
(millions per 

year) Percent 

Operating costs: 

Coal at 55 per ton 

Catalyst and chemicals 

Operating labor 

Overhead.. 

Mai ntena nee at 4 percent 

Local taxes and insurance at 1H percent 

Income tax (48 percent). 

Capital return (15 percent DCF) 



Revenues needed 

Revenues: 

Aviation jet fuel at 76 cents per gallon 

Motor Gasoline at 69 cents per gallon... 

Fuel Oil at 85 cents per gallon 

Olefins 

Fuel gases 

Oxygenated chemicals 

Sulfur 

BTX, gasoline and oil 

Total 346.0 100.0 



$30. 19 


8.7 


3.04 


.9 


3.45 


1.0 


4.0 


1.2 


31.3 


9.1 


11.7 


3.4 


107.0 


30.9 


155. 


44.8 


346.0 


100.0 


99.0 


28.6 


48.4 


14.0 


51.1 


14.8 


29.4 


8.5 


32.5 


9.4 


54.9 


15.8 


6.9 


2.0 


24.0 


6.9 



24 

If the price of coal delivered to the SASOL-Synthol plant were to 
rise from $5 per ton to $10 per ton, which does not appear to be ex- 
pected, the effect of this would be to increase jet fuel price from 76 
cents per gallon to 86 cents per gallon at a 15 percent DCF rate of 
return. Thus a doubling of coal price would have a much smaller 
effect (10 cents per gallon) on jet fuel price than an increase to 20 
percent DCF rate of return which would lead to a jet fuel price 
increment of 39 cents per gallon. Jet fuel cost is much more sensitive 
to financial factors than it is to coal price because of the very high 
capital intensity of the operation and, also, the relatively good thermal 
efficiency. 

The proposed operation can, however, make jet fuel as well as other 
important fuels and chemicals from domestic coal. Such an operation 
can minimize disruption to domestic aviation, both military and 
civilian, that could result from future oil embargoes particularly as 
imported oil grows in its share of the domestic market. Should this 
factor be considered important enough for the national security, it 
becomes of interest to examine the cost relationships if the plant 
investment is treated as an item of national defense and no capital 
return is judged necessary. The total annual operating costs drop to 
$84 million dollars per year and income from the petrochemicals will 
be $114 million dollars per year. This assumes no income from the 
aviation jet fuel, motor gasoline, fuel o : l and fuel gases. Thus a 
Government-built plant could be operated under contract permitting 
supply of fuels to the Government at no cost and leaving a potential 
income to the operator of some $30 million per year for purchasing 
coal under contract, operating the complex plant and marketing the 
wide spectrum of chemicals. This interesting possibility is but one of 
many and again illustrates the effect of the high capital intensity of 
the process. 

The production of the plant is about 9,400 barrels per day of jet fuel 
which is about 2 percent of the military jet fuel used in the United 
States. If 20 percent of the military fuel were to be supplied it would 
be necessary to build ten of the proposed plants for a total plant 
investment of about $8 billion dollars. 

Should ten such plants be built, the quantity of co-products to be 
produced and sold are listed in Table 4 and compared with recent 
figures on national production of these materials. It may be seen that 
the national markets can absorb the co-product output in most cases 
without undue disruption of commerce in these materials. But in the 
case of ethyl alcohol, the output of ten plants would equal the total 
current industrial production. It would be unacceptable to release so 
much new material into the market and it will be necessary, therefore, 
to find another outlet. Such an outlet can be the jet fuel itself, into 
which the ethanol can be blended. This may well be undesirable 
because of water solubility induced by ethanol. Such water solubility 
appears unacceptable because it would probably raise the freezing 
point above the — 58°F specification. If, however, the ethyl alcohol 
were to be converted to esters or ethers, this advantage would be 
overcome. Such a solution, however, would lower the heating value of 
the jet fuel because of the oxygen content and would decrease the 
aircraft range for a given weight of fuel. Another, and possibly better, 
solution would be blending of ethanol into the fuel oil where it should 



25 

make a boiler fuel of superior quality because of its freedom from 
sulfur content. Protection of such fuel against water freezing problems 
should be relatively simple in boiler fuel applications. Still another 
option is available. Ethanol can be converted to motor gasoline using 
a recently-announced process now under development. This gasoline 
could be absorbed by the motor fuel market quite easily. 

TABLE 4.— MODIFIED SASOL-SYNTHOL PLANT; OUTPUT OF COPRODUCT CHEMICALS 



Output, millions of 


pounds 


National 


per year 




capacity 


1 


10 


(Millions of 


plant 


plants 


pounds 
per y-ear) 


79.1 


791 


23, 500 


342.0 


3,420 


9,821 


138.0 


1,380 . 




6.4 


64 


1,500 


1.7 


17 


6,660 


19.7 


197 


2,015 


7.3 


73 


5,056 


216.0 


2,160 


2,120 


47.8 


478 . 




6.6 


66 


115 


16.0 


160 


551 


23.2 


232 . 




36.0 


360 


2,265 


8.2 


82 


60 


5.7 


57 . 




384.0 


3,840 


23, 600 


294.0 


2,990 


24, 290 



Ethylene 

Propylene 

Butyiene-butanes 

Acetaldehy de 

Methanol 

Acetone 

Methylethyl ketone.. 

Ethanol 

Propanol 

Isobutanol.. 

Normal butanol 

Heavy alcohols 

Acetic acid 

Propionic acid. 

Higher acids... 

Sulfur 

Benzene, toluene, and xylene 

In short, disposal of the chemicals should be no impediment for 
operation of a single plant and, indeed, may provide an attractive 
incentive for contract operation of a Government-owned facility. But 
for operation of 10 plants to supply some 20% of the Nation's military 
aviation jet fuel, it will be necessary to consider and select from 
several alternates for disposal of ethyl alcohol co-product. 

If polymerization and aromatics blending were to be used, aviation 
jet fuel would increase from 9,400 to 11,000 barrels per day and 8 
rather than 10 plants would be needed to supply about 20 percent of 
the military jet fuel. The cost of eight plants would be about $6.5 
billion dollars and the problem of disposing of ethanol would be 
eased somewhat, though not eliminated. 

Aviation jet fuel supply can also be insulated from imported oil 
embargoes even though it is made from domestic petroleum if im- 
ported petroleum were to be replaced by fuels from oil shale, tar sands, 
secondary or tertiary oil recovery, coal liquefaction to made syncrude 
or coal gasification for high or low Btu gas to replace oil uses. These 
alternate approaches, in general, have the same characteristics as the 
proposed jet fuel operation. They require very high capital invest- 
ments and fuels made by these alternate approaches are also very 
heavily burdened by capital return requirements characteristic of 
commercial operations. At the current state of development of these 
alternate technologies, the uncertainties in capital requirements appear 
large enough so that it is not truly possible to determine the relative 
economics of the several approaches. It does appear that the na- 
tional interest in developing energy independence or energy supply 
assurance would be best served by constructing and operating demon- 



26 

stration plants of each alternate approach, including the SASOL- 
Synthol approach. This would provide basic cost data on the economics 
of the various technologies so that a sound selection of the most 
economically advantageous processes can be made when the switch to 
domestic resources must be faced. The cost of such a program is not 
small, but it can be repaid very rapidly because it will permit selection 
of the most economic method of using indigenous resources. 

8. Conclusions 

The SASOL plant in South Africa has been producing motor gaso- 
line as primary product along with a large number of co-products. 
Aviation jet fuel, however, is not one of the co-products and thr 
SASOL operation, therefore, does not provide commercial demonstra- 
tion of the production of jet fuel from coal. 

Aviation jet fuel differs from SASOL gasoline in the following 
respects. Aviation fuel must have (1) a higher boiling range and the 
associated higher flash point, (2) less than 1 percent olefins compared 
to a very olefinic SASOL gasoline and (3) a much lower freezing 
point specification of — 58°F. The Synthol process, which accounts 
for the bulk of the SASOL production, can be modified to make jet 
fuel boiling range material as a major product. This conclusion is 
available from pilot plant data accumulated during development of 
the Synthol process in the Research Department of Pullman Kellogg. 
Information from this program has provided a basis for estimating 
the product slate and properties of the raw jet fuel fraction when 
operating to make aviation fuel boiling range material. The raw 
material must then be hydrogenated and isomerized to meet existing 
ASTM aviation fuel standards for olefins and freezing point. 

A commercial -scale plant making jet fuel and associated co-products 
from coal using the general SASOL approach but modified, as indi- 
cated, for aviation product is expected to require a plant investment 
of $780 million when making 9,400 barrels per day of jet fuel from 
17,100 tons per day of coal. This preliminary estimate shows the 
proposed operation to be very capital intensive. In fact some 76 per- 
cent of the total operating costs are associated with capital charges 
to earn 15 percent on the plant investment on a discounted cash 
flow basis and to pay income tax on the needed return. As a result 
of these capital -related factors, aviation jet fuel would have to be 
sold at 76 cents per gallon and the operation bears a very heavy 
burden as long as aviation jet fuel from petroleum is available at 30 
to 34 cents per gallon. 

If production of aviation jet fuel from coal were to be justified on a 
national security basis it is possible to consider operation of a Govern- 
ment-owned plant on which return on capital investment is not re- 
quired in contrast to the situation with commercial operation. One 
option under these circumstances would be to contract out the opera- 
tion of the plant to a company that could assume the entire operation 
of the plant, provide the aviation jet fuel to the United States at 
no cost and perform these services in return for the chemical co- 
products as its incentive. 

This arrangement appears attractive for a single plant of the size 
selected but such a plant provides only some 2 percent of the national 



27 

military jet fuel requirement. Should ten such plants be contemplated 
to meet 20 percent of military aviation fuel needs, the volume of 
ethanol produced would be so great as to disrupt these markets and 
remove this incentive, which is a major component of the suggested 
incentive for the proposed operator. This problem could be handled 
by further processing the ethanol for blending into aviation fuel or 
by blending it directly into fuel oil. These options would reduce the 
income from chemical co-products and would require income from 
aviation fuel or the other fuels to restore the contract operator's 
incentive. It is of interest to note, in this connection, that erosion of 
co-product chemical income to 50 percent of the income in Tables 
2 and 3 can be made up by a charge of about 8 cents per gallon for 
aviation jet fuel, motor gasoline and fuel oil turned back to the 
Government. 

Thus it is concluded that commercial operation of a modified 
SASOL-Synthol process to make aviation jet fuel from coal is not 
attractive, but arrangements appear possible to operate such a facility 
with Government supply of the needed capital for national security 
considerations. 

o 



UNIVERSITY OF FLORIDA 



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